Vulcanization of vinyl resins



d Sept. 9, 1947 VULCANIZATION OF VINYL RESINS Louis F. Reuter, Akron,

B. F. Goodrich Compa corporation of New Yo Ohio, asslgnor to The ny, New York, N. Y., a rk No Drawing. Application February 11, 1944, Serial No. 521,973

Claims.

This invention relates to the vulcanization of vinyl resins and pertains more specifically to the vulcanization of such resins in the presence of certain modifying agents which produce compo" sitions having greatly improved properties.

As is well-known, various polymers of the halogenated ethylenes may be plasticized with certain plasticizers to give rubbery plastic products possessing properties which render them valuable as substitutes for rubber. They also have certain properties which render them superior to rubber for many uses. Among the polymers which have been thus employed are those made from, vinyl chloride, vinylidene chloride, vinyl bromide, vinylidene bromide and mixtures of these monomers with one another, as well as with lesser proportions of other copolymerizable monomers such as vinyl acetate, vinyl propionate, vinyl butyrate, methyl acrylate, methyl methacrylate, ethyl acrylate, methyl ethacrylate, and other similar materials. One of the outstanding properties of these plasticized polymeric compositions is that they are permanently thermoplastic, that is, that they may be repeatedly softened by heating to a temperature well above room temperature. It is also known that the thermoplasticity of these polymeric compositions may be greatly reduced or completely eliminated by heating the composition with a small amount of a basic nitrogen-containing organic compound. Because this reduction of thermoplasticity is analogous with the change which occurs in rubber when it is vulcanized, the process has been termed vulcanization, and the materials employed have been termed vulcanizing agents. Such vulcanizing agents have been disclosed by Alexander, U. S. Patent 2,117,591 issued May 17, 1938, and in my copending applications, Serial Nos. 506,268; 506,- 269; 506,270 and 506,271, filed October 14, 1943. it is pointed out in these cases that from 0.5 to 10% of the vulcanizing agent may be used in the composition. They comprise a wide variety of basic nitrogen-containing organic compounds such as the condensation products of aliphatic aldehydes with aromatic amines or with ammonia, as well as guanidines and guanidine salts, aromatic polyamines, aliphatic polyamines, cinchona alkaloids, dihydroquinolines, and the like.

'Although these vulcanizing agents are quite efiective in reducing the thermoplasticity of the ,olasticized vinyl polymers, their use is attended with certain disadvantages. The vulcanized compositions have an undesirable odor, tend to be iarit in color, and tend to deteriorate rapidly with age. I have now discovered that these disadvantages can be overcome by incorporating in the composition, together with the vulcanlzlng agents, a small amount of an organic compound containing a plurality of functionally hydroxyl groups. By the term functionally hydroxyl group" I mean a hydroxyl group which does not form a part of another functional group, as it does, for example, in a carboxylic group. For the sake of convenience I have termed these compounds modifying agents. Although I have found that any organic compound containing a plurality of hydroxyl groups may be employed, best results are obtained with compounds which, except for the oxygen of the hydroxyl group, contain only carbon and hydrogen. Among the compounds which may be employed are ethylene glycol, diethylene glycol, propylene glycol, trimethylene glycol, glycerine, erythritol, arabitol,

xylitol, mannitol, sorbitol, glucose, lactose, su-.

crose, cellulose, polyvinyl alcohol, triethanolamine, inosltol, qulnic acid; monoesters oi glycerine with organic acids, such as the glycerine monoester of cottonseed fatty acid, stearic acid, palmitic acid, caprylic acid, or even acetic acid; 11?- droquinone, bromohydroquinone, chlorohydroquinone, 2,3-dlmethyl hydroquinone, resorcinol, hexylresorcinol. pyrocatechol, phloroglucinol, gallic acid, pyrogallol, and the like.

The polymers with which my new modifying agents may be used include all of those with which the above-mentioned vulcanizing agents are efl'ective, that is, with the polymers made by the polymerization of monomeric materlals consisting predominantly of a halogenated ethylene in which from one to two halogen atoms are attached to one only of the carbon atoms. Although as little as 0.05% of my new modifying agent based upon the weight of the polymer may be effective, I have found that the best results are obtained by using from about one to about five percent or more. The amount and type of plasticizer employed in the composition is not critical, although, of course, the softness and resiliency of the stock depend to a large extent upon the particular plasticizer employed. In general, useful compositions may be secured by using from about 20 to 150 parts or more of plasticizer for each parts of polymer. Any. of the usual plasticizers may be employed, such as tricresyl phosphate, dibutyl phthalate, dioctyl phthalate, ditetrahydrofurfuryl sebacate, dicapryl phthalate, butyl phthalyl butyl glycollate, undecyl tetrahydronaphthyl ketone, cyclohexyl obenzoylbenzoate, or the like.

The use of my new modifying agents serves not only to prevent deterioratiohzof the vulcanized compositions and prevent the formation of undesirable color and odor, but serves also to increase greatly the ultimate elongation of the vulcanized compositions, and to increase their resistance to tear, especially at elevated temperatures. Vulcanized compositions made with my modifying agentsalso exhibit a remarkably increased flexibility at low temperature and increased resistance to organic solvents over similar compositions vulcanized without my modifying agents.

The modifying agent may be added together with the plasticizer and the vulcanizing agent to the polymer either on a hot roll mill or in an internal mixer, or the mixture of vulcanizing agent, plasticizer, and modifying agent may be added to an emulsionor solution of the polymer. If desired, the plasticizer may be first incorporated in the polymer and the vulcanizing agent and modifying agent added to the plasticized composition either together or separately. The composition may then be vulcanized in the usual manner by heating to an elevated temperature for a substantial period of time. Although the temperature and time of vulcanization varywith the amount and type of plasticizer employed, as

be employed in my new vulcanizable composition without deleterious eilects.

The following examples are given merely for the purpose of illustrating the nature of my invention and are not to be construed as'a limitation.

Example I A plasticized polymer composition was prepared by mixing 100 parts by weight of high molecular weight polyvinyl chloride, 70 parts by weight of butyl phthalyl butyl glycollate, and five parts of magnesium oxide on a hot roll mill. To this composition there were added as vulcanizing agent three parts of the condensation product of butyraldehyde and aniline described by Alexander, U. S. Patent 2,117,591 issued May 1'7, 1938. Similar compositions were prepared, to which there were added, respectively, one part and three parts by weight of resorcinol. All three compositions were then vulcanized bgheating in a press for 20 minutes at 340 F. The ultimate tensile strength of all three vulcanized compositions was about 1800 lbs. per sq. in. However, the ultimate elongation of the composition containing no modifying agent was only 200%, whereas the composition containing one part of resorcinol had an ultimate elongation of 310%, and the composition containing three parts of resorcinol had an elongation of 400%. Both of the compositions containing resorcinol had a much higher tear resistance than did the composition containing no resorcinol. The thermoplasticity of all three compositions was so greatly'reduced that the product could be removed from the mold before cooling, but th latter two were much lighter in color than the first.

Example II A series of compositions similar to those described in Example I was prepared, one containing no modifying agent, the second containing one part of glycerine, and the third containing three parts of glycerine. They were vulcanized by heating in a press for 30 minutes at 330 F. All three had an ultimate tensile strength of about 2,000 lbs. per sq. in. However, the ultimate elongations were 130, 240 and 400%, respectively. The tear resistance of the latter two compositions was very much higher than that of the composition containing no modifying agent and whereas the former composition was darkcolored and possessed an undesirable odor, the latter two were almost free from color and free from odor. The latter two compositions also retained their flexibility at much lower temperatures than did the former.

Example III Three compositions similar to those of Example I were prepared; the first containing no modify- Example IV A composition containing 100 parts by weight of high molecular weight polyvinyl chloride, parts of butyl phthalyl butyl glycollate, 5 parts of the condensation product of butyraldehyde and aniline, and 5 parts of magnesium oxide, was prepared as described in Example I. To one portion of this composition there were added five parts of sorbitol. The two compositions were then vulcanized by heating in a press for 30 minutes at 330 F. and their physical properties were then determined. The ultimate tensile strength of each was about the same, but the ultimate elongation of the composition containing no modifying agent was only 130%, whereas that of the composition containing sorbitol was 300%. The color, odor, tear resistance, and low-temperature flexibility 'of the composition containing the modifying agent were also much superior to those of the composition containing no modifying agent.

The thermoplasticity of all of the compositions described in the preceding specific. examples was reduced to such an extent by the vulcanization process that all of the compositions could readily be removed from the hot mold. When no magnesium oxide pigment used in these examples is not an essential ingredient of the composition; it may be replaced by other suitable pigments or may be omitted entirely. A,

These newvulcanized compositions are useful 2,427,071 r 6 for not only all the purposes to which the vulbon radical and a plurality of attached hydroxyl canized plasticized vinyl resin compositions heregroups is a polyhydroxy benzene. tofore known have been put, but they are par- 6. A vulcanized composition prepared by the tioularly valuable because of their high elongamethod of claim 5. tion, their high tear resistance, their resistance '7. The process of claim 1 wherein the plastito solvents, and their flexibility at low temper- 5 cized polymer composition is one having as a atures. base polyvinyl chloride.

Although I have herein described specific em- 8. A vulcanized composition prepared by the bodiments of my invention, I do not intend to method 01' claim '7. restrict myself solely thereto, but'to include all m 9. The process of vulcanizing a plasticlzed oi the modifications embraced within the spirit P lym r composition havin as a base p y scope f the appended clainm prepared by the polymerization of a monomeric I claim: material comprising predominantly a halogenated 1, Th process of vulcanizing plasticized ethylene containing from 1 to 2 halogen atoms polymer composition having as a ba a, polymer on one only of the carbon atoms, which comprepared by t polymeflzaflon of a monomeric prises incorporating in said composition from 0.5 material comprising predominantly a halogent0 by W ight based on the polymer of a ated ethylene containing f om one to two ha1 basic nitrogen-containing organic compound seexclusively of a hydrocarbon radical containing en am 0 one on] of the carbon atoms, which lected from the class consisting of condensation 5 z f m SM d composition from products of ahphatic aldehydes with aromatic 05 to 10% by weight based on the polymer of 0 amines and condensation products of aliphatic d d aldehydes with ammonia, and from 0.05 to 5% z ig ggg gg g g gg aggfl g g g by weight based on the polymer of an organic compound composed exclusively of a hydrocarbon the Polymer of an organic compound composed radical containing from 2 to 6 carbon atoms and a plurality of hydroxyl groups attached to dif- 'fl 2 t0 6 carbon atoms and plurality of ferent carbon atoms, and then heating the rehydroxyl groups at c diflerent suiting composition at a temperature of 300 to atoms, and then h atin h resulting composi- 350 F. for a time of 10 to 100 minutes.

tion at a temperat re f 300 to for a i 10. A vulcanized composition prepared by the of 10 to 100 minutes. process ofclaim 9.

2. A vulcanized composition prepared by the LOUIS F. REU'IER,

7 method of claim 1.

3. The process of claim 1 wherein the organic REFERENCES CITED comm exclusively of a hydrocarbon The followin references are of recor in he radical and a plurality of attached hydroxyl m of this patgent: d t groups is glycerine.

4. A vulcanized composition prepared by the Um STATES PATENTS method of claim 3. Number Name Date 5. The process of claim 1 wherein the organic 2,117,591 Alexander May 17, 1938 compound composed exclusively of a hydrocar- 40 2,103,581 Gray Dec. 28, 1937 

